This invention relates to cryogenic cooling apparatus and, more particularly, to cooling apparatus having a heat sink of thermally conductive material which has a relatively high specific heat for storage of thermal energy, wherein the heat sink is connectable by a diffuser plate of low specific heat and high diffusivity to a relatively small hot object which is to be cooled.
There are numerous situations where a hot small object is to be cooled by apparatus which is much larger physically than the object to be cooled. One situation of particular interest is the cooling of a semiconductor laser. A particular application of the cooling apparatus applies to a semiconductor laser used to radiate high power in a military situation. Therefore, while it is to be understood that the cooling apparatus of the present invention is applicable for cooling many types of hot objects, it is advantageous to show use of the cooling apparatus in the miltary situation which will now be described.
Jamming of an infrared heat seeking missile, for the purpose of protecting a friendly aircraft, has been accomplished by transmitting a beam of infrared radiation wherein the radiation amplitude is modulated in the manner of a train of pulses. Such a beam of amplitude modulated, or chopped, radiation is directed at the missile. As is well known, such missiles have a detector assembly which responds to incident radiation to produce a detected signal. The missiles are operative to detect a direction of incident radiation of substantially constant amplitude by a process of chopping the detected signal to gain phase data which directs the missile in the azimuthal and the elevation coordinates for tracking a source of the radiation. The presence of a jamming chopped infrared signal introduces additional pulses to the missile's detected signal resulting in the development of directional errors which drive the missile off course.
A problem arises with the use of cryogrenic cooling apparatus of the prior art in that such apparatus has significant weight which reduces the flight capabilities of an aircraft. A further aspect of the problem of presently available cryogenic cooling apparatus is that the apparatus is physically much larger than a relatively small semiconductor laser which is to be cooled. As a result, inefficiencies exist in the transference of heat from the small hot object to the large cooling apparatus.